java - 如何正确检测碰撞？

Question

这是我第一次使用 LibGDX 制作游戏，当两个东西发生碰撞时，我试图提高我的游戏分数，但它根本没有记录碰撞。

这是我在 Player 类中的内容:

import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.TextureRegion;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.BodyDef;
import com.badlogic.gdx.physics.box2d.CircleShape;
import com.badlogic.gdx.physics.box2d.EdgeShape;
import com.badlogic.gdx.physics.box2d.FixtureDef;
import com.badlogic.gdx.physics.box2d.World;
import com.mygdx.summative.MyGdxGame;
import com.mygdx.summative.Screens.PlayScreen;

public class Player extends Sprite {

public World world;
public Body b2dbody;
private TextureRegion peteStand;

public Player(World world, PlayScreen screen ){
    super(screen.getAtlas().findRegion("goomba"));
    this.world = world;
    definePlayer();
    peteStand = new TextureRegion(getTexture(), 227,1,16,16);
    setBounds(227,1,16/ MyGdxGame.PPM,16/MyGdxGame.PPM);
    setRegion(peteStand);
}

public void update (float dt ){
    setPosition(b2dbody.getPosition().x - getWidth() /2, b2dbody.getPosition().y - getHeight()/2);
}

public void definePlayer (){
    BodyDef bdef = new BodyDef();
    bdef.position.set(32 / MyGdxGame.PPM,32 /MyGdxGame.PPM);
    bdef.type = BodyDef.BodyType.DynamicBody;
    b2dbody = world.createBody(bdef);

    FixtureDef fdef = new FixtureDef();
    CircleShape shape = new CircleShape();
    shape.setRadius(6/MyGdxGame.PPM);

    fdef.shape = shape;
    b2dbody.createFixture(fdef);

    EdgeShape body = new EdgeShape(); // used for collision dectection
    body.set(new Vector2(-1/MyGdxGame.PPM,7/MyGdxGame.PPM), new Vector2(1/MyGdxGame.PPM,7/MyGdxGame.PPM)); // sets up borders for collision on player
    fdef.shape = body ;
    fdef.isSensor = true;
    b2dbody.createFixture(fdef).setUserData("body");   // used to identify collisions to see if one if the player
}

}

当云来袭的时候，我想增加分数，所以我在Object类中这样写:

public class Cloud extends InteractiveTileObject {

public Cloud(World world, TiledMap map, Rectangle bounds) {
    super(world, map, bounds);
    fixture.setUserData(this);
}

@Override
public void onBodyHit() {
    Gdx.app.log("Cloud" , "Collision");
    Hud.addScore(200);
}
}

我错过了什么？这是 ContactListener 类中的联系方法:

    @Override
public void beginContact(Contact contact) {     // when to things start to collide

    // figures out with fixture is which in a collision of two objects
    Fixture fixA = contact.getFixtureA();
    Fixture fixB = contact.getFixtureB();

    // checks of one is players body
    if (fixA.getUserData() == "body" || fixB.getUserData() == "body"){
        Fixture body = fixA.getUserData() == "body" ? fixA : fixB;
        Fixture object = body == fixA ? fixB : fixA;

        // checks if the object the player collided with is a interactive object
        if (object.getUserData() instanceof InteractiveTileObject) {
            ((InteractiveTileObject) object.getUserData() ).onBodyHit();
        }

    }
}

Answer 1

通常，fixA.getUserData() == "body" 是错误的，因为您比较的是引用的相等性。要检查 String 在内容方面是否等于另一个字符串，即按字典顺序，您应该执行 fixA.getUserData().equals("body") 或更安全的方法"body".equals(fixA.getUserData()).

顺便说一句，“玩家” 标识符可能更合适，因为从技术上讲，物理世界中的一切都是一个物体。